1. Field of the Invention
The present invention relates generally to a multi-channel optical signal transmission system for optical communication, and more particularly to a method for correcting the shift of an output wavelength generated when the intensity of output light of a light source is adjusted by a drive current of the light source in a multi-channel light source driving apparatus used in an optical communication system.
2. Description of the Related Art
Generally, optical communication technologies using optical fiber enable high speed and large capacity information transmission and do not cause signal interference or crosstalk due to electromagnetic induction, so they have been used in international communications through submarine cables. Recently, with the development of multiplexing technology and network technology, optical communication has been greatly extended in its application range to a backbone network for voice and data communications between private exchanges, and high speed wide band multimedia communications including cable television, video on demand (VOD), etc.
Typically, in optical communication, optical signals with different wavelengths, generated by and outputted from a plurality of laser diodes, are modulated, and the optical signals with different wavelengths are multiplexed and are transmitted to a destination through a predetermined optical line as a multiplexed optical signal. Further, at the destination, the multiplexed and transmitted optical signal is demultiplexed, such that a plurality of original optical signals with different wavelengths are restored from the multiplexed optical signal. At this time, in an optical communication system, certain specifications are proposed for the intensity of output light of a laser diode used as a light source, for example, a Distributed FeedBack-Laser Diode (DFB-LD), the wavelength of output light, the line width of the output light, a side mode suppression ratio, etc. Of these specifications, the intensity and wavelength of output light are varied in their characteristics according to a drive current by which the DFB-LD is driven and a drive temperature at which the DFB-LD is driven. For example, if the drive current is increased so as to increase the intensity of output light, the wavelength of output light is shifted to a long wavelength; while if the drive current is decreased so as to decrease the intensity of output light, the wavelength of output light is shifted to a short wavelength. As described above, if the wavelength is not uniform, original data cannot be easily restored at a corresponding destination, thus hindering normal information transmission.
In order to prevent such a wavelength shift phenomenon and maintain a uniform wavelength, a method of locking a wavelength continuously using a wavelength locker or wavelength measuring device is used in the prior art. A wavelength locking apparatus and method continuously using such a wavelength locker or wavelength measuring device is disclosed in U.S. Pat. No. 6,369,926, U.S. Pat. No. 6,144,025, U.S. Pat. No. 6,043,915, and Korean Pat. Appl. No. 10-1998-0015193.
However, the above method of locking a wavelength continuously using the wavelength locker or wavelength measuring device is problematic in that its implementation algorithm is complicated, and the operating cost of an optical signal transmission system is increased due to the continuous use of the wavelength locker or the wavelength measuring device.